I've had the same problems. One way to work around this problem is to make the dynamic panel a bit bigger (so it overlaps the other grid) - then choose "send to back". It will then be placed behind the other grid and elements - but will still be visible because you made it slightly bigger. In that way you can always access it and choose "Bring to front"
I hope this made it clear. It's not the perfect solution, but an acceptable workaround...